Making remote IPs appear on local network for testing.

Okay so here is the scenario. We are testing our product internally and the software uses IP addresses in the URLs. The are hard coded in the product so what we would like to do is set up our machines in a way that when it calls the URL at http://123.45.678.9, it actually forwards this request to a web server at 192.168.1.145 which is a QA test server.

Obviously, the devs can't rebuild the product every time because we need it "final". Any idea how we can trick our machines into doing this? I think the hosts file will do this for domains, but not IPs?